In aerosol containers and the like, the dispensing valve is normally mounted to the container through the use of a valve mounting assembly comprising a mounting cup and an associated gasket. The mounting assembly includes a gasket receiving channel which is positioned over and clinched to the rolled rim of the container about the upper end thereof. The mounting cup is typically clinched to the upper part of the container by a device which displaces radially outwardly the cylindrical wall of the mounting cup.
Much effort has been directed to the provision of the gasket or gasket seal within the cup to ensure a positive sealing of the cup to the container in a manner which minimizes loss of the pressurized contents.
In its simplest form, the gasket can comprise a conventional flat rubber washer or annular gasket which is loosely received about the central body of the cup and sits freely within the channel. Such gaskets are relatively expensive and could, due to the relatively loose reception within the mounting cup, be displaced during the handling of the mounting assembly prior to and during the final securement to the container. Such gaskets are especially susceptible of movement during the propellant filling operation and during valve assembly, impairing the clinching operation. In addition, pre-cut gaskets generally reside only in the receiving channel of the mounting cup and do not provide a seal in the critical area at which the mounting cup is clinched to the container.
A more common type of gasket currently in commercial use is a "flowed-in" gasket in which a liquid solvent-based gasket-forming composition is deposited in the channel, caused to flow over the surfaces thereof, the solvent evaporated from the material, and the remaining material cured. This is an expensive procedure requiring multiple production steps including the use of curing ovens or other means for effecting the drying and curing of the gasket material, and solvent removal means such as hoods and venting ductwork, in the case of non-aqueous solvents. Further, means must be provided for rotating the mounting cup beneath a metering apparatus which dispenses carefully determined amounts of gasket-forming composition. The mounting cup must be handled carefully to maintain it in a horizontal position before the gasket solidifies. The resulting gasket tends to be of nonuniform thickness in the clinch area of the cup and container. U.S. Pat. No. 3,342,381 (Simons et al) discloses a "flowed-in" gasket.
Another technique for disposing a gasket on the mounting cup is described in U.S. Pat. No. 3,417,177 (Simons et al). That patent discloses a method comprising positioning a circular band of heat-shrinkable material over a portion of the cylindrical wall of the mounting cup and thereafter heating the cup to shrink the band of material into contact with the cup wall.
U.S. Pat. No. 3,443,006 (Simons, et al) discloses a method wherein a band of gasket material is swelled into place using a suitable swelling agent.
The heat shrinking and swelling methods are time consuming and require relatively expensive equipment to either heat the material or to recover swelling agent.
Another form of gasket currently in use is a sleeve gasket involving a tube of low density polyethylene which is inserted around the central cylindrical body, extended at least partially into the annular channel, and then cut to the proper length. Such a sleeve gasket has some advantages over the aforedescribed gaskets in the elimination of the complex and time consuming curing and solvent removal procedures. However, the procedures and equipment involved in the utilization of an extruded polyethylene tube are complex, particularly if an intimate, frictional engagement of the sleeve gasket with the body wall is to be achieved. The tube insertion and cutting operations must be carefully performed to properly seat the tube onto the mounting cup. It is difficult to dispose the polyethylene tube more than about halfway into the receiving channel. European Patent Application No. 81300339.9 more fully discloses the use of polyethylene tubes to form gaskets.